Measuring Ecosystems. Ehringer. Worldwide productivity.
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Measuring Ecosystems Ehringer
Worldwide productivity • The best current estimate of global net primary productivity is 90 to 120 * 1,000,000,000 tons dry weight per year in terrestrial habitats, and 50 to 60 * 1,000,000,000 tons per year in oceanic communities. Estimates of productivity are lowest in the deserts (0-1 kcal/m/yr. or 90 g/m/yr.) and highest in the tropical rain forest (+20 kcal/m/yr. or 2200 g/m/yr.).
per square meter • Tropical rain forest • Coral Reefs • Estuaries ]
for the planet as a whole • Open ocean • Tropical rain forests • Grasslands and pastures
Measurements • Species richness • Species diversity • Keystone species • Habitat • Niche
Simpson’s index • The most common formula for working out Species Diversity is the Simpson's diversity index, which uses the following formula: • D=N(N-1)/Σn(n-1) • Where: D = diversity index N = Total number of organisms of all species found n = number of individuals of a particular species • A high D value suggests a stable and ancient site, while a low D value could suggest a polluted site, recent colonization or agricultural management. • Usually used in studies of vegetation but can also be applied to animals.
Shannon Index • The advantage of this index is that it takes into account the number of species and the evenness of the species. The index is increased either by having additional unique species, or by having a greater species evenness
Alpha, Beta, and Gamma Diversity • Alpha diversity refers to the diversity within a particular area or ecosystem, and is usually expressed by the number of species (i.e., species richness) in that ecosystem. • If we examine the change in species diversity between these ecosystems then we are measuring the beta diversity. We are counting the total number of species that are unique to each of the ecosystems being compared. • Gamma diversity is a measure of the overall diversity for the different ecosystems within a region.
Keystone species • A keystone species is a species whose very presence contributes to a diversity of life and whose extinction would consequently lead to the extinction of other forms of life. Keystone species help to support the ecosystem (entire community of life) of which they are a part. • Sea otters in kelp forests keep sea urchins in check. Kelp roots are merely anchors, and not the vast nutrient gathering networks of land plants. Thus the urchins only need to eat the roots of the kelp, a tiny fraction of the plant's biomass, to remove it from the ecosystem.
Foundation species • A foundation species is a dominant primary producer in an ecosystem both in terms of abundance and influence. Examples include kelp in kelp forests and corals in coral reefs.
Indicator species • An indicator species is any biological species that defines a trait or characteristic of the environment. For example, a species may delineate an ecoregion or indicate an environmental condition such as a disease outbreak, pollution, species competition or climate change. Indicator species can be among the most sensitive species in a region, acting as an early warning to monitoring biologists.
Flagship species • A flagship species is a species chosen to represent an environmental cause, such as an ecosystem in need of conservation. These species are chosen for their vulnerability, attractiveness or distinctiveness in order to best engender support and acknowledgement from the public at large • Examples of flagship species include the giant panda of China, the golden lion tamarin of Brazil's Atlantic coastal forest, the Indian tiger, the African elephant, the mountain gorilla of Central Africa, the orangutan of Southeast Asia, and the leatherback sea turtle.